1. Field of the Invention
The present invention relates to a clockspring connector for electrically interconnecting a fixed member and a movable member of an automotive steering system or the like by a flexible cable.
2. Description of the Prior Art
A clockspring connector for interconnecting a fixed member and a movable member movable relative to the fixed member by a flexible cable is employed in electrically connecting a movable member capable of rotating by a limited number of turns and a fixed member of an automotive steering system. The ratio of the cost of the flexible cable to the total cost of the clockspring connector of this kind is large. A clockspring connector proposed in U.S. Pat. No. 4,540,223 is intended to reduce its cost by reducing the length of the flexible cable included therein.
As shown in FIG. 9, the clockspring connector proposed in U.S. Pat. No. 4,540,223 has a cylindrical fixed member 100, a movable member 101 mounted for rotation on the fixed cylindrical member 100, and a flexible cable 103 contained in an annular space 102 formed between the fixed member 100 and the movable member 101. The opposite ends of the flexible cable 103 is fastened respectively to the fixed member 100 and the movable member 101. The winding direction of the flexible cable 103 is inverted at its U-shaped inverting portion 103a in the annular space 102. An intermediate movable member 104 having a shape resembling the letter C in a plan view is nested in the annular space 102 so as to be movable in circumferential directions. The inverting portion 103a of the flexible cable 103 is wound around a roller 105 supported for rotation on one open end of the intermediate movable member 104.
When the movable member 101 is turned clockwise as viewed in FIG. 9, the inverting portion 103a of the flexible cable 103 moves in a circumferential direction within the annular space 102, so that the number of coils of the flexible cable 103 wound on the outer cylinder of the fixed member 100 increases and hence the flexible cable is unwound. On the contrary, when the movable member 101 is turned counterclockwise, the inverting portion 103a of the flexible cable 103 moves in the same direction, so that the flexible cable 103 is taken up on the movable member 101 and the number of coils of the flexible cable 103 wound on the inner cylinder of the movable member 101 increases. When the flexible cable 103 is thus unwound or taken up, the intermediate movable member 104 is moved in the same direction by the force applied thereto by the inverting portion 103a.
In this prior art clockspring connector, the direction of winding the flexible cable 103 on the inner cylinder and that of winding the flexible cable 103 on the outer cylinder 101 are opposite to each other. Therefore, the length of the flexible cable 103 is far less than that of a flexible cable included in an equivalent clockspring connector in which the flexible cable is wound in a spiral coils and hence the cost of the former clockspring connector is lower than that of the latter clockspring connector. Since the intermediate movable member is disposed between a portion of the flexible cable wound on the inner cylinder and a portion of the flexible cable wound on the outer cylinder and the inverting portion of the flexible cable is wound around the roller supported for rotation on one end of the intermediate movable member, the flexible cable can be wound on the inner cylinder or the outer cylinder by the inverting portion in winding or unwinding the flexible cable.
However, in winding or unwinding the flexible cable, the flexible cable tends to expand radially. For example, when the movable member is turned in a direction to wind the flexible cable on the inner cylinder, a portion of the flexible cable extending between the outer cylinder and the inverting portion expands slightly radially inward (toward the inner cylinder) and touches the outer circumference of the movable member and, when the movable member is turned in a direction to wind the flexible cable on the outer cylinder, a portion of the flexible cable extending between the inner cylinder and the inverting portion expands slightly radially outward (toward the outer cylinder) and touches the inner circumference of the movable member. In either case, the flexible cable is unable to advance smoothly toward the inverting position due to the frictional resistance of the movable member.